Re: New system? (PS3, XBOX, Wii)
If you are solely interested in playing sports games by yourself (Not online), and want a conventional gaming experience, I would go 360. I have the 360 and the Wii.
While the Wii is fun to play games like Madden on, it's more of a novelty. After a while the intrigue of swinging your arms around to actually play the game wears off.
The PS3 is what you should go with if you're interested in Blu-Ray enough, but other than that it's basically a more expensive 360 (If we're just talking sports games available for all three consoles). Oh and yes, if you want to play PS2 titles bad too that's a plus with the system.
The reason I would choose the 360, for you, though, is it's cheaper than the PS3 for just gaming. Meaning if you want to go out, purchase a system with Madden and start a franchise you'll pay less for the 360 than the PS3, but get basically equal graphics capability (Madden also runs at a higher frame rate on the 360), but at the same time, you won't be getting the (In my opinion) watered down versions of the Wii.
I believe you can update rosters for games with a Silver (free) live account on the Xbox. I could be wrong about that though as I subscribe to gold membership.
Honestly for someone who just wants to play sports games offline as it sounds like you do, there really isn't a wrong answer. It just all depends on the price you want to pay and a few other preferences such as control method.
Good luck with whatever you decide!